Hello, I m Dr. Branch, thanks for using Ask a Doctor . After the first trimester, MEBEX is considered safe and recommended for treatment of worms. No harm has been shown to be caused by MEBEX to babies; however, untreated worms has been shown to harm babies, and so I would encourage you to take the medicine as prescribed by your doctor. I hope that helps, please let me know if you have any other questions about that, and I would be glad to discuss it with you further.